This time next year, as you’re keenly aware, you will no longer be the mayor of New York. We all know how much you love the job, and how much you’ll miss it. No question about it: Though you have had your critics (including, at times, me), you’ve been a very good mayor.

They say that you’re thinking a lot these days about what to do next. When you step down you’ll be 71, and plenty vital enough to do something significant. And of course, with a net worth of $20 billion or so, you certainly have the financial wherewithal to affect the issues that are important to you. You showed it in the last election, ginning up a super PAC and spending around $10 million on a handful of elections across the country where you thought your money could make a difference. Even though you got into the game late, you won more than you lost.

I know you have lots of interests, but after listening to you these past few weeks — ever since the horrible massacre in Newtown, Conn. — I am hoping you will direct your post-mayoral energies to one issue: gun control. There is, quite simply, no one else in America who has a better chance of moving the country toward a saner gun policy than you. It is an effort worthy of your talents, and your money.

First, there is your obvious passion for the issue. They say it was your experience as mayor that sensitized you to the issue — and how could it not, with the funerals you’ve had to attend, and the mothers of murdered children you’ve had to console? Since the Newtown tragedy, no other high-profile politician has been as forceful in condemning gun violence and demanding “immediate action” in Congress. Millions of Americans — indeed, a majority of them — agree with you. They are looking for somebody to lead the charge against the National Rifle Association.

Second, though your message has been blunt, your tactics have been politically shrewd. In 2006, you started a new organization to fight gun violence: Mayors Against Illegal Guns. You thought that mayors had the credibility to reframe the issue as one of crime control, rather than gun control. Mayors Against Illegal Guns now has more than 800 mayors, and nearly 1 million “active supporters.” It has lobbyists in Washington and elsewhere, and has had success resisting recent NRA legislative initiatives. Its short-term agenda — ban assault weapons, require background checks for all gun sales, make gun trafficking a federal crime, and so on — is a good, sensible place to start regulating guns.

Third — and let’s not be coy here — you’re rich. The NRA has an annual budget that is reported to be $300 million. In 2011, the combined budgets of all the groups trying to prevent gun violence came to around $16 million. The best-known of those groups, the Brady Campaign to Prevent Gun Violence, has seen its support and its funding dwindle in recent years. Meanwhile, the NRA and its allies have done a brilliant job at pushing through laws that make it nearly impossible to prevent gun violence. There are more than 200 members of Congress who regularly get a perfect score from the NRA. It is going to take money to change that because money is what Congress responds to.

To be honest, Mr. Mayor, I wish you could start tomorrow. With each passing day, the urgency that accompanied the Newtown shooting slips further away. President Barack Obama, who seems absolutely terrified to take on the gun lobby, didn’t even mention guns when asked about his second-term priorities. Mitch McConnell, the Senate minority leader, has said that the first months of the new congressional session will be devoted to the issue of federal spending. Guns, he said, will just have to wait.

In recent years, even in states that experienced horrific mass killings, gun laws have only become looser. In Virginia, the state Legislature repealed a law that barred people from buying more than one handgun a month, and passed a law “to allow permit holders to carry concealed and loaded weapons into bars and restaurants,” according to ProPublica. That same article reported that in Texas, two years after the Fort Hood shooting, legislators “gave gun carriers greater freedom to take their weapons to more places.” The only two gun bills Obama has signed were laws that expanded gun rights. “The country needs his leadership,” you said of Obama after he announced that Vice President Joe Biden was going to lead a panel making a new effort to reduce gun violence.

With all due respect, sir, what the country needs is your leadership on this issue. The sooner the better.